Figure 16.23 shows a STN for the simple
mobile phone described in scenarios A and B on the
web.

(a) Identify any missing transitions
and suggest possible behaviour that would be sensible
for the user.

(b) Scenarios C and D demonstrate the
additional behaviour of the new phone. Update the
STN in Figure 16.23 to add the new store and recall
facilities of the new phone. Where there is not sufficient
information in the scenarios choose suitable behaviour.
You can use ellipses ( ) where you would expect
major additional functionality (e.g. storing numbers);
don't attempt to fully specify such additional functions.
List and briefly describe and justify any such design
decisions that are required or any other design issues
that become apparent.